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Instance Public methods
add_check_constraint(table_name, expression, if_not_exists: false, **options) Link
Adds a new check constraint to the table. expression
is a String
representation of verifiable boolean condition.
add_check_constraint :products, "price > 0", name: "price_check"
generates:
ALTER TABLE "products" ADD CONSTRAINT price_check CHECK (price > 0)
The options
hash can include the following keys:
:name
-
The constraint name. Defaults to
chk_rails_<identifier>
. :if_not_exists
-
Silently ignore if the constraint already exists, rather than raise an error.
:validate
-
(PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to
true
.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1293 def add_check_constraint(table_name, expression, if_not_exists: false, **options) return unless supports_check_constraints? options = check_constraint_options(table_name, expression, options) return if if_not_exists && check_constraint_exists?(table_name, **options) at = create_alter_table(table_name) at.add_check_constraint(expression, options) execute schema_creation.accept(at) end
add_column(table_name, column_name, type, **options) Link
Add a new type
column named column_name
to table_name
.
See ActiveRecord::ConnectionAdapters::TableDefinition.column.
The type
parameter is normally one of the migrations native types, which is one of the following: :primary_key
, :string
, :text
, :integer
, :bigint
, :float
, :decimal
, :numeric
, :datetime
, :time
, :date
, :binary
, :blob
, :boolean
.
You may use a type not in this list as long as it is supported by your database (for example, “polygon” in MySQL
), but this will not be database agnostic and should usually be avoided.
Available options are (none of these exists by default):
-
:comment
- Specifies the comment for the column. This option is ignored by some backends. -
:collation
- Specifies the collation for a:string
or:text
column. If not specified, the column will have the same collation as the table. -
:default
- The column’s default value. Usenil
forNULL
. -
:limit
- Requests a maximum column length. This is the number of characters for a:string
column and number of bytes for:text
,:binary
,:blob
, and:integer
columns. This option is ignored by some backends. -
:null
- Allows or disallowsNULL
values in the column. -
:precision
- Specifies the precision for the:decimal
,:numeric
,:datetime
, and:time
columns. -
:scale
- Specifies the scale for the:decimal
and:numeric
columns. -
:if_not_exists
- Specifies if the column already exists to not try to re-add it. This will avoid duplicate column errors.
Note: The precision is the total number of significant digits, and the scale is the number of digits that can be stored following the decimal point. For example, the number 123.45 has a precision of 5 and a scale of 2. A decimal with a precision of 5 and a scale of 2 can range from -999.99 to 999.99.
Please be aware of different RDBMS implementations behavior with :decimal
columns:
-
The SQL standard says the default scale should be 0,
:scale
<=:precision
, and makes no comments about the requirements of:precision
. -
MySQL:
:precision
[1..65],:scale
[0..30]. Default is (10,0). -
PostgreSQL:
:precision
[1..infinity],:scale
[0..infinity]. No default. -
SQLite3: No restrictions on
:precision
and:scale
, but the maximum supported:precision
is 16. No default. -
Oracle:
:precision
[1..38],:scale
[-84..127]. Default is (38,0). -
SqlServer:
:precision
[1..38],:scale
[0..38]. Default (38,0).
Examples
add_column(:users, :picture, :binary, limit: 2.megabytes)
# ALTER TABLE "users" ADD "picture" blob(2097152)
add_column(:articles, :status, :string, limit: 20, default: 'draft', null: false)
# ALTER TABLE "articles" ADD "status" varchar(20) DEFAULT 'draft' NOT NULL
add_column(:answers, :bill_gates_money, :decimal, precision: 15, scale: 2)
# ALTER TABLE "answers" ADD "bill_gates_money" decimal(15,2)
add_column(:measurements, :sensor_reading, :decimal, precision: 30, scale: 20)
# ALTER TABLE "measurements" ADD "sensor_reading" decimal(30,20)
# While :scale defaults to zero on most databases, it
# probably wouldn't hurt to include it.
add_column(:measurements, :huge_integer, :decimal, precision: 30)
# ALTER TABLE "measurements" ADD "huge_integer" decimal(30)
# Defines a column that stores an array of a type.
add_column(:users, :skills, :text, array: true)
# ALTER TABLE "users" ADD "skills" text[]
# Defines a column with a database-specific type.
add_column(:shapes, :triangle, 'polygon')
# ALTER TABLE "shapes" ADD "triangle" polygon
# Ignores the method call if the column exists
add_column(:shapes, :triangle, 'polygon', if_not_exists: true)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 636 def add_column(table_name, column_name, type, **options) add_column_def = build_add_column_definition(table_name, column_name, type, **options) return unless add_column_def execute schema_creation.accept(add_column_def) end
add_foreign_key(from_table, to_table, **options) Link
Adds a new foreign key. from_table
is the table with the key column, to_table
contains the referenced primary key.
The foreign key will be named after the following pattern: fk_rails_<identifier>
. identifier
is a 10 character long string which is deterministically generated from the from_table
and column
. A custom name can be specified with the :name
option.
Creating a simple foreign key
add_foreign_key :articles, :authors
generates:
ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id")
Creating a foreign key, ignoring method call if the foreign key exists
add_foreign_key(:articles, :authors, if_not_exists: true)
Creating a foreign key on a specific column
add_foreign_key :articles, :users, column: :author_id, primary_key: "lng_id"
generates:
ALTER TABLE "articles" ADD CONSTRAINT fk_rails_58ca3d3a82 FOREIGN KEY ("author_id") REFERENCES "users" ("lng_id")
Creating a composite foreign key
Assuming "carts" table has "(shop_id, user_id)" as a primary key.
add_foreign_key :orders, :carts, primary_key: [:shop_id, :user_id]
generates:
ALTER TABLE "orders" ADD CONSTRAINT fk_rails_6f5e4cb3a4 FOREIGN KEY ("cart_shop_id", "cart_user_id") REFERENCES "carts" ("shop_id", "user_id")
Creating a cascading foreign key
add_foreign_key :articles, :authors, on_delete: :cascade
generates:
ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id") ON DELETE CASCADE
The options
hash can include the following keys:
:column
-
The foreign key column name on
from_table
. Defaults toto_table.singularize + "_id"
. Pass an array to create a composite foreign key. :primary_key
-
The primary key column name on
to_table
. Defaults toid
. Pass an array to create a composite foreign key. :name
-
The constraint name. Defaults to
fk_rails_<identifier>
. :on_delete
-
Action that happens
ON DELETE
. Valid values are:nullify
,:cascade
, and:restrict
:on_update
-
Action that happens
ON UPDATE
. Valid values are:nullify
,:cascade
, and:restrict
:if_not_exists
-
Specifies if the foreign key already exists to not try to re-add it. This will avoid duplicate column errors.
:validate
-
(PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to
true
. :deferrable
-
(PostgreSQL only) Specify whether or not the foreign key should be deferrable. Valid values are booleans or
:deferred
or:immediate
to specify the default behavior. Defaults tofalse
.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1173 def add_foreign_key(from_table, to_table, **options) return unless use_foreign_keys? return if options[:if_not_exists] == true && foreign_key_exists?(from_table, to_table, **options.slice(:column)) options = foreign_key_options(from_table, to_table, options) at = create_alter_table from_table at.add_foreign_key to_table, options execute schema_creation.accept(at) end
add_index(table_name, column_name, **options) Link
Adds a new index to the table. column_name
can be a single Symbol
, or an Array
of Symbols.
The index will be named after the table and the column name(s), unless you pass :name
as an option.
Creating a simple index
add_index(:suppliers, :name)
generates:
CREATE INDEX index_suppliers_on_name ON suppliers(name)
Creating a index which already exists
add_index(:suppliers, :name, if_not_exists: true)
generates:
CREATE INDEX IF NOT EXISTS index_suppliers_on_name ON suppliers(name)
Note: Not supported by MySQL
.
Creating a unique index
add_index(:accounts, [:branch_id, :party_id], unique: true)
generates:
CREATE UNIQUE INDEX index_accounts_on_branch_id_and_party_id ON accounts(branch_id, party_id)
Creating a named index
add_index(:accounts, [:branch_id, :party_id], unique: true, name: 'by_branch_party')
generates:
CREATE UNIQUE INDEX by_branch_party ON accounts(branch_id, party_id)
Creating an index with specific key length
add_index(:accounts, :name, name: 'by_name', length: 10)
generates:
CREATE INDEX by_name ON accounts(name(10))
Creating an index with specific key lengths for multiple keys
add_index(:accounts, [:name, :surname], name: 'by_name_surname', length: {name: 10, surname: 15})
generates:
CREATE INDEX by_name_surname ON accounts(name(10), surname(15))
Note: only supported by MySQL
Creating an index with a sort order (desc or asc, asc is the default)
add_index(:accounts, [:branch_id, :party_id, :surname], name: 'by_branch_desc_party', order: {branch_id: :desc, party_id: :asc})
generates:
CREATE INDEX by_branch_desc_party ON accounts(branch_id DESC, party_id ASC, surname)
Note: MySQL
only supports index order from 8.0.1 onwards (earlier versions accepted the syntax but ignored it).
Creating a partial index
add_index(:accounts, [:branch_id, :party_id], unique: true, where: "active")
generates:
CREATE UNIQUE INDEX index_accounts_on_branch_id_and_party_id ON accounts(branch_id, party_id) WHERE active
Note: Partial indexes are only supported for PostgreSQL and SQLite.
Creating an index that includes additional columns
add_index(:accounts, :branch_id, include: :party_id)
generates:
CREATE INDEX index_accounts_on_branch_id ON accounts USING btree(branch_id) INCLUDE (party_id)
Note: only supported by PostgreSQL.
Creating an index where NULLs are treated equally
add_index(:people, :last_name, nulls_not_distinct: true)
generates:
CREATE INDEX index_people_on_last_name ON people (last_name) NULLS NOT DISTINCT
Note: only supported by PostgreSQL version 15.0.0 and greater.
Creating an index with a specific method
add_index(:developers, :name, using: 'btree')
generates:
CREATE INDEX index_developers_on_name ON developers USING btree (name) -- PostgreSQL
CREATE INDEX index_developers_on_name USING btree ON developers (name) -- MySQL
Note: only supported by PostgreSQL and MySQL
Creating an index with a specific operator class
add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops)
# CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL
add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops })
# CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL
add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops)
# CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL
Note: only supported by PostgreSQL
Creating an index with a specific type
add_index(:developers, :name, type: :fulltext)
generates:
CREATE FULLTEXT INDEX index_developers_on_name ON developers (name) -- MySQL
Note: only supported by MySQL
.
Creating an index with a specific algorithm
add_index(:developers, :name, algorithm: :concurrently)
# CREATE INDEX CONCURRENTLY developers_on_name on developers (name) -- PostgreSQL
add_index(:developers, :name, algorithm: :inplace)
# CREATE INDEX `index_developers_on_name` ON `developers` (`name`) ALGORITHM = INPLACE -- MySQL
Note: only supported by PostgreSQL and MySQL
.
Concurrently adding an index is not supported in a transaction.
For more information see the “Transactional Migrations” section.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 915 def add_index(table_name, column_name, **options) create_index = build_create_index_definition(table_name, column_name, **options) execute schema_creation.accept(create_index) end
add_reference(table_name, ref_name, **options) Link
Adds a reference. The reference column is a bigint by default, the :type
option can be used to specify a different type. Optionally adds a _type
column, if :polymorphic
option is provided.
The options
hash can include the following keys:
:type
-
The reference column type. Defaults to
:bigint
. :index
-
Add an appropriate index. Defaults to true. See
add_index
for usage of this option. :foreign_key
-
Add an appropriate foreign key constraint. Defaults to false, pass true to add. In case the join table can’t be inferred from the association pass
:to_table
with the appropriate table name. :polymorphic
-
Whether an additional
_type
column should be added. Defaults to false. :null
-
Whether the column allows nulls. Defaults to true.
Create a user_id bigint column without an index
add_reference(:products, :user, index: false)
Create a user_id string column
add_reference(:products, :user, type: :string)
Create supplier_id, supplier_type columns
add_reference(:products, :supplier, polymorphic: true)
Create a supplier_id column with a unique index
add_reference(:products, :supplier, index: { unique: true })
Create a supplier_id column with a named index
add_reference(:products, :supplier, index: { name: "my_supplier_index" })
Create a supplier_id column and appropriate foreign key
add_reference(:products, :supplier, foreign_key: true)
Create a supplier_id column and a foreign key to the firms table
add_reference(:products, :supplier, foreign_key: { to_table: :firms })
add_timestamps(table_name, **options) Link
Adds timestamps (created_at
and updated_at
) columns to table_name
. Additional options (like :null
) are forwarded to add_column
.
add_timestamps(:suppliers, null: true)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1459 def add_timestamps(table_name, **options) fragments = add_timestamps_for_alter(table_name, **options) execute "ALTER TABLE #{quote_table_name(table_name)} #{fragments.join(', ')}" end
assume_migrated_upto_version(version) Link
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1364 def assume_migrated_upto_version(version) version = version.to_i sm_table = quote_table_name(pool.schema_migration.table_name) migration_context = pool.migration_context migrated = migration_context.get_all_versions versions = migration_context.migrations.map(&:version) unless migrated.include?(version) execute "INSERT INTO #{sm_table} (version) VALUES (#{quote(version)})" end inserting = (versions - migrated).select { |v| v < version } if inserting.any? if (duplicate = inserting.detect { |v| inserting.count(v) > 1 }) raise "Duplicate migration #{duplicate}. Please renumber your migrations to resolve the conflict." end execute insert_versions_sql(inserting) end end
build_create_table_definition(table_name, id: :primary_key, primary_key: nil, force: nil, **options) Link
Returns a TableDefinition
object containing information about the table that would be created if the same arguments were passed to create_table
. See create_table
for information about passing a table_name
, and other additional options that can be passed.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 333 def build_create_table_definition(table_name, id: :primary_key, primary_key: nil, force: nil, **options) table_definition = create_table_definition(table_name, **options.extract!(*valid_table_definition_options, :_skip_validate_options)) table_definition.set_primary_key(table_name, id, primary_key, **options.extract!(*valid_primary_key_options, :_skip_validate_options)) yield table_definition if block_given? table_definition end
change_column(table_name, column_name, type, **options) Link
Changes the column’s definition according to the new options. See TableDefinition#column
for details of the options you can use.
change_column(:suppliers, :name, :string, limit: 80)
change_column(:accounts, :description, :text)
change_column_comment(table_name, column_name, comment_or_changes) Link
Changes the comment for a column or removes it if nil
.
Passing a hash containing :from
and :to
will make this change reversible in migration:
change_column_comment(:posts, :state, from: "old_comment", to: "new_comment")
change_column_default(table_name, column_name, default_or_changes) Link
Sets a new default value for a column:
change_column_default(:suppliers, :qualification, 'new')
change_column_default(:accounts, :authorized, 1)
Setting the default to nil
effectively drops the default:
change_column_default(:users, :email, nil)
Passing a hash containing :from
and :to
will make this change reversible in migration:
change_column_default(:posts, :state, from: nil, to: "draft")
change_column_null(table_name, column_name, null, default = nil) Link
Sets or removes a NOT NULL
constraint on a column. The null
flag indicates whether the value can be NULL
. For example
change_column_null(:users, :nickname, false)
says nicknames cannot be NULL
(adds the constraint), whereas
change_column_null(:users, :nickname, true)
allows them to be NULL
(drops the constraint).
The method accepts an optional fourth argument to replace existing NULL
s with some other value. Use that one when enabling the constraint if needed, since otherwise those rows would not be valid.
Please note the fourth argument does not set a column’s default.
change_table(table_name, base = self, **options) Link
A block for changing columns in table
.
# change_table() yields a Table instance
change_table(:suppliers) do |t|
t.column :name, :string, limit: 60
# Other column alterations here
end
The options
hash can include the following keys:
:bulk
-
Set this to true to make this a bulk alter query, such as
ALTER TABLE `users` ADD COLUMN age INT, ADD COLUMN birthdate DATETIME ...
Defaults to false.
Only supported on the
MySQL
and PostgreSQL adapter, ignored elsewhere.
Add a column
change_table(:suppliers) do |t|
t.column :name, :string, limit: 60
end
Change type of a column
change_table(:suppliers) do |t|
t.change :metadata, :json
end
Add 2 integer columns
change_table(:suppliers) do |t|
t.integer :width, :height, null: false, default: 0
end
Add created_at/updated_at columns
change_table(:suppliers) do |t|
t.timestamps
end
Add a foreign key column
change_table(:suppliers) do |t|
t.references :company
end
Creates a company_id(bigint)
column.
Add a polymorphic foreign key column
change_table(:suppliers) do |t|
t.belongs_to :company, polymorphic: true
end
Creates company_type(varchar)
and company_id(bigint)
columns.
Remove a column
change_table(:suppliers) do |t|
t.remove :company
end
Remove several columns
change_table(:suppliers) do |t|
t.remove :company_id
t.remove :width, :height
end
Remove an index
change_table(:suppliers) do |t|
t.remove_index :company_id
end
See also Table
for details on all of the various column transformations.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 510 def change_table(table_name, base = self, **options) if supports_bulk_alter? && options[:bulk] recorder = ActiveRecord::Migration::CommandRecorder.new(self) yield update_table_definition(table_name, recorder) bulk_change_table(table_name, recorder.commands) else yield update_table_definition(table_name, base) end end
change_table_comment(table_name, comment_or_changes) Link
Changes the comment for a table or removes it if nil
.
Passing a hash containing :from
and :to
will make this change reversible in migration:
change_table_comment(:posts, from: "old_comment", to: "new_comment")
check_constraint_exists?(table_name, **options) Link
Checks to see if a check constraint exists on a table for a given check constraint definition.
check_constraint_exists?(:products, name: "price_check")
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1341 def check_constraint_exists?(table_name, **options) if !options.key?(:name) && !options.key?(:expression) raise ArgumentError, "At least one of :name or :expression must be supplied" end check_constraint_for(table_name, **options).present? end
check_constraints(table_name) Link
Returns an array of check constraints for the given table. The check constraints are represented as CheckConstraintDefinition objects.
column_exists?(table_name, column_name, type = nil, **options) Link
Checks to see if a column exists in a given table.
# Check a column exists
column_exists?(:suppliers, :name)
# Check a column exists of a particular type
#
# This works for standard non-casted types (eg. string) but is unreliable
# for types that may get cast to something else (eg. char, bigint).
column_exists?(:suppliers, :name, :string)
# Check a column exists with a specific definition
column_exists?(:suppliers, :name, :string, limit: 100)
column_exists?(:suppliers, :name, :string, default: 'default')
column_exists?(:suppliers, :name, :string, null: false)
column_exists?(:suppliers, :tax, :decimal, precision: 8, scale: 2)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 132 def column_exists?(table_name, column_name, type = nil, **options) column_name = column_name.to_s checks = [] checks << lambda { |c| c.name == column_name } checks << lambda { |c| c.type == type.to_sym rescue nil } if type column_options_keys.each do |attr| checks << lambda { |c| c.send(attr) == options[attr] } if options.key?(attr) end columns(table_name).any? { |c| checks.all? { |check| check[c] } } end
columns(table_name) Link
Returns an array of Column
objects for the table specified by table_name
.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 107 def columns(table_name) table_name = table_name.to_s definitions = column_definitions(table_name) definitions.map do |field| new_column_from_field(table_name, field, definitions) end end
create_join_table(table_1, table_2, column_options: {}, **options) Link
Creates a new join table with the name created using the lexical order of the first two arguments. These arguments can be a String
or a Symbol
.
# Creates a table called 'assemblies_parts' with no id.
create_join_table(:assemblies, :parts)
# Creates a table called 'paper_boxes_papers' with no id.
create_join_table('papers', 'paper_boxes')
A duplicate prefix is combined into a single prefix. This is useful for namespaced models like Music::Artist and Music::Record:
# Creates a table called 'music_artists_records' with no id.
create_join_table('music_artists', 'music_records')
You can pass an options
hash which can include the following keys:
:table_name
-
Sets the table name, overriding the default.
:column_options
-
Any extra options you want appended to the columns definition.
:options
-
Any extra options you want appended to the table definition.
:temporary
-
Make a temporary table.
:force
-
Set to true to drop the table before creating it. Defaults to false.
Note that create_join_table
does not create any indices by default; you can use its block form to do so yourself:
create_join_table :products, :categories do |t|
t.index :product_id
t.index :category_id
end
Add a backend specific option to the generated SQL (MySQL
)
create_join_table(:assemblies, :parts, options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8')
generates:
CREATE TABLE assemblies_parts (
assembly_id bigint NOT NULL,
part_id bigint NOT NULL,
) ENGINE=InnoDB DEFAULT CHARSET=utf8
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 389 def create_join_table(table_1, table_2, column_options: {}, **options) join_table_name = find_join_table_name(table_1, table_2, options) column_options.reverse_merge!(null: false, index: false) t1_ref, t2_ref = [table_1, table_2].map { |t| reference_name_for_table(t) } create_table(join_table_name, **options.merge!(id: false)) do |td| td.references t1_ref, **column_options td.references t2_ref, **column_options yield td if block_given? end end
create_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options, &block) Link
Creates a new table with the name table_name
. table_name
may either be a String
or a Symbol
.
There are two ways to work with create_table
. You can use the block form or the regular form, like this:
Block form
# create_table() passes a TableDefinition object to the block.
# This form will not only create the table, but also columns for the
# table.
create_table(:suppliers) do |t|
t.column :name, :string, limit: 60
# Other fields here
end
Block form, with shorthand
# You can also use the column types as method calls, rather than calling the column method.
create_table(:suppliers) do |t|
t.string :name, limit: 60
# Other fields here
end
Regular form
# Creates a table called 'suppliers' with no columns.
create_table(:suppliers)
# Add a column to 'suppliers'.
add_column(:suppliers, :name, :string, {limit: 60})
The options
hash can include the following keys:
:id
-
Whether to automatically add a primary key column. Defaults to true. Join tables for ActiveRecord::Base.has_and_belongs_to_many should set it to false.
A
Symbol
can be used to specify the type of the generated primary key column. :primary_key
-
The name of the primary key, if one is to be added automatically. Defaults to
id
. If:id
is false, then this option is ignored.If an array is passed, a composite primary key will be created.
Note that Active Record models will automatically detect their primary key. This can be avoided by using self.primary_key= on the model to define the key explicitly.
:options
-
Any extra options you want appended to the table definition.
:temporary
-
Make a temporary table.
:force
-
Set to true to drop the table before creating it. Set to
:cascade
to drop dependent objects as well. Defaults to false. :if_not_exists
-
Set to true to avoid raising an error when the table already exists. Defaults to false.
:as
-
SQL to use to generate the table. When this option is used, the block is ignored, as are the
:id
and:primary_key
options.
Add a backend specific option to the generated SQL (MySQL
)
create_table(:suppliers, options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8mb4')
generates:
CREATE TABLE suppliers (
id bigint auto_increment PRIMARY KEY
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
Rename the primary key column
create_table(:objects, primary_key: 'guid') do |t|
t.column :name, :string, limit: 80
end
generates:
CREATE TABLE objects (
guid bigint auto_increment PRIMARY KEY,
name varchar(80)
)
Change the primary key column type
create_table(:tags, id: :string) do |t|
t.column :label, :string
end
generates:
CREATE TABLE tags (
id varchar PRIMARY KEY,
label varchar
)
Create a composite primary key
create_table(:orders, primary_key: [:product_id, :client_id]) do |t|
t.belongs_to :product
t.belongs_to :client
end
generates:
CREATE TABLE orders (
product_id bigint NOT NULL,
client_id bigint NOT NULL
);
ALTER TABLE ONLY "orders"
ADD CONSTRAINT orders_pkey PRIMARY KEY (product_id, client_id);
Do not add a primary key column
create_table(:categories_suppliers, id: false) do |t|
t.column :category_id, :bigint
t.column :supplier_id, :bigint
end
generates:
CREATE TABLE categories_suppliers (
category_id bigint,
supplier_id bigint
)
Create a temporary table based on a query
create_table(:long_query, temporary: true,
as: "SELECT * FROM orders INNER JOIN line_items ON order_id=orders.id")
generates:
CREATE TEMPORARY TABLE long_query AS
SELECT * FROM orders INNER JOIN line_items ON order_id=orders.id
See also TableDefinition#column
for details on how to create columns.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 293 def create_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options, &block) validate_create_table_options!(options) validate_table_length!(table_name) unless options[:_uses_legacy_table_name] if force && options.key?(:if_not_exists) raise ArgumentError, "Options `:force` and `:if_not_exists` cannot be used simultaneously." end td = build_create_table_definition(table_name, id: id, primary_key: primary_key, force: force, **options, &block) if force drop_table(table_name, force: force, if_exists: true) else schema_cache.clear_data_source_cache!(table_name.to_s) end result = execute schema_creation.accept(td) unless supports_indexes_in_create? td.indexes.each do |column_name, index_options| add_index(table_name, column_name, **index_options, if_not_exists: td.if_not_exists) end end if supports_comments? && !supports_comments_in_create? if table_comment = td.comment.presence change_table_comment(table_name, table_comment) end td.columns.each do |column| change_column_comment(table_name, column.name, column.comment) if column.comment.present? end end result end
data_source_exists?(name) Link
Checks to see if the data source name
exists on the database.
data_source_exists?(:ebooks)
data_sources() Link
drop_join_table(table_1, table_2, **options) Link
Drops the join table specified by the given arguments. See create_join_table
and drop_table
for details.
Although this command ignores the block if one is given, it can be helpful to provide one in a migration’s change
method so it can be reverted. In that case, the block will be used by create_join_table
.
drop_table(*table_names, **options) Link
Drops a table or tables from the database.
:force
-
Set to
:cascade
to drop dependent objects as well. Defaults to false. :if_exists
-
Set to
true
to only drop the table if it exists. Defaults to false.
Although this command ignores most options
and the block if one is given, it can be helpful to provide these in a migration’s change
method so it can be reverted. In that case, options
and the block will be used by create_table
except if you provide more than one table which is not supported.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 540 def drop_table(*table_names, **options) table_names.each do |table_name| schema_cache.clear_data_source_cache!(table_name.to_s) execute "DROP TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}" end end
foreign_key_exists?(from_table, to_table = nil, **options) Link
Checks to see if a foreign key exists on a table for a given foreign key definition.
# Checks to see if a foreign key exists.
foreign_key_exists?(:accounts, :branches)
# Checks to see if a foreign key on a specified column exists.
foreign_key_exists?(:accounts, column: :owner_id)
# Checks to see if a foreign key with a custom name exists.
foreign_key_exists?(:accounts, name: "special_fk_name")
foreign_keys(table_name) Link
Returns an array of foreign keys for the given table. The foreign keys are represented as ForeignKeyDefinition objects.
index_exists?(table_name, column_name, **options) Link
Checks to see if an index exists on a table for a given index definition.
# Check an index exists
index_exists?(:suppliers, :company_id)
# Check an index on multiple columns exists
index_exists?(:suppliers, [:company_id, :company_type])
# Check a unique index exists
index_exists?(:suppliers, :company_id, unique: true)
# Check an index with a custom name exists
index_exists?(:suppliers, :company_id, name: "idx_company_id")
# Check a valid index exists (PostgreSQL only)
index_exists?(:suppliers, :company_id, valid: true)
index_name_exists?(table_name, index_name) Link
Verifies the existence of an index with a given name.
indexes(table_name) Link
Returns an array of indexes for the given table.
max_index_name_size() Link
Returns the maximum length of an index name in bytes.
native_database_types() Link
Returns a hash of mappings from the abstract data types to the native database types. See TableDefinition#column
for details on the recognized abstract data types.
options_include_default?(options) Link
primary_key(table_name) Link
Returns just a table’s primary key
remove_belongs_to(table_name, ref_name, foreign_key: false, polymorphic: false, **options) Link
remove_check_constraint(table_name, expression = nil, if_exists: false, **options) Link
Removes the given check constraint from the table. Removing a check constraint that does not exist will raise an error.
remove_check_constraint :products, name: "price_check"
To silently ignore a non-existent check constraint rather than raise an error, use the if_exists
option.
remove_check_constraint :products, name: "price_check", if_exists: true
The expression
parameter will be ignored if present. It can be helpful to provide this in a migration’s change
method so it can be reverted. In that case, expression
will be used by add_check_constraint
.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1324 def remove_check_constraint(table_name, expression = nil, if_exists: false, **options) return unless supports_check_constraints? return if if_exists && !check_constraint_exists?(table_name, **options) chk_name_to_delete = check_constraint_for!(table_name, expression: expression, **options).name at = create_alter_table(table_name) at.drop_check_constraint(chk_name_to_delete) execute schema_creation.accept(at) end
remove_column(table_name, column_name, type = nil, **options) Link
Removes the column from the table definition.
remove_column(:suppliers, :qualification)
The type
and options
parameters will be ignored if present. It can be helpful to provide these in a migration’s change
method so it can be reverted. In that case, type
and options
will be used by add_column
. Depending on the database you’re using, indexes using this column may be automatically removed or modified to remove this column from the index.
If the options provided include an if_exists
key, it will be used to check if the column does not exist. This will silently ignore the migration rather than raising if the column was already removed.
remove_column(:suppliers, :qualification, if_exists: true)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 699 def remove_column(table_name, column_name, type = nil, **options) return if options[:if_exists] == true && !column_exists?(table_name, column_name) execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, **options)}" end
remove_columns(table_name, *column_names, type: nil, **options) Link
Removes the given columns from the table definition.
remove_columns(:suppliers, :qualification, :experience)
type
and other column options can be passed to make migration reversible.
remove_columns(:suppliers, :qualification, :experience, type: :string, null: false)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 675 def remove_columns(table_name, *column_names, type: nil, **options) if column_names.empty? raise ArgumentError.new("You must specify at least one column name. Example: remove_columns(:people, :first_name)") end remove_column_fragments = remove_columns_for_alter(table_name, *column_names, type: type, **options) execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_fragments.join(', ')}" end
remove_foreign_key(from_table, to_table = nil, **options) Link
Removes the given foreign key from the table. Any option parameters provided will be used to re-add the foreign key in case of a migration rollback. It is recommended that you provide any options used when creating the foreign key so that the migration can be reverted properly.
Removes the foreign key on accounts.branch_id
.
remove_foreign_key :accounts, :branches
Removes the foreign key on accounts.owner_id
.
remove_foreign_key :accounts, column: :owner_id
Removes the foreign key on accounts.owner_id
.
remove_foreign_key :accounts, to_table: :owners
Removes the foreign key named special_fk_name
on the accounts
table.
remove_foreign_key :accounts, name: :special_fk_name
Checks if the foreign key exists before trying to remove it. Will silently ignore indexes that don’t exist.
remove_foreign_key :accounts, :branches, if_exists: true
The options
hash accepts the same keys as SchemaStatements#add_foreign_key
with an addition of
:to_table
-
The name of the table that contains the referenced primary key.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1214 def remove_foreign_key(from_table, to_table = nil, **options) return unless use_foreign_keys? return if options.delete(:if_exists) == true && !foreign_key_exists?(from_table, to_table) fk_name_to_delete = foreign_key_for!(from_table, to_table: to_table, **options).name at = create_alter_table from_table at.drop_foreign_key fk_name_to_delete execute schema_creation.accept(at) end
remove_index(table_name, column_name = nil, **options) Link
Removes the given index from the table.
Removes the index on branch_id
in the accounts
table if exactly one such index exists.
remove_index :accounts, :branch_id
Removes the index on branch_id
in the accounts
table if exactly one such index exists.
remove_index :accounts, column: :branch_id
Removes the index on branch_id
and party_id
in the accounts
table if exactly one such index exists.
remove_index :accounts, column: [:branch_id, :party_id]
Removes the index named by_branch_party
in the accounts
table.
remove_index :accounts, name: :by_branch_party
Removes the index on branch_id
named by_branch_party
in the accounts
table.
remove_index :accounts, :branch_id, name: :by_branch_party
Checks if the index exists before trying to remove it. Will silently ignore indexes that don’t exist.
remove_index :accounts, if_exists: true
Removes the index named by_branch_party
in the accounts
table concurrently
.
remove_index :accounts, name: :by_branch_party, algorithm: :concurrently
Note: only supported by PostgreSQL.
Concurrently removing an index is not supported in a transaction.
For more information see the “Transactional Migrations” section.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 966 def remove_index(table_name, column_name = nil, **options) return if options[:if_exists] && !index_exists?(table_name, column_name, **options) index_name = index_name_for_remove(table_name, column_name, options) execute "DROP INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)}" end
remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) Link
Removes the reference(s). Also removes a type
column if one exists.
Remove the reference
remove_reference(:products, :user, index: false)
Remove polymorphic reference
remove_reference(:products, :supplier, polymorphic: true)
Remove the reference with a foreign key
remove_reference(:products, :user, foreign_key: true)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1082 def remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) conditional_options = options.slice(:if_exists, :if_not_exists) if foreign_key reference_name = Base.pluralize_table_names ? ref_name.to_s.pluralize : ref_name if foreign_key.is_a?(Hash) foreign_key_options = foreign_key.merge(conditional_options) else foreign_key_options = { to_table: reference_name, **conditional_options } end foreign_key_options[:column] ||= "#{ref_name}_id" remove_foreign_key(table_name, **foreign_key_options) end remove_column(table_name, "#{ref_name}_id", **conditional_options) remove_column(table_name, "#{ref_name}_type", **conditional_options) if polymorphic end
remove_timestamps(table_name, **options) Link
Removes the timestamp columns (created_at
and updated_at
) from the table definition.
remove_timestamps(:suppliers)
rename_column(table_name, column_name, new_column_name) Link
Renames a column.
rename_column(:suppliers, :description, :name)
rename_index(table_name, old_name, new_name) Link
Renames an index.
Rename the index_people_on_last_name
index to index_users_on_last_name
:
rename_index :people, 'index_people_on_last_name', 'index_users_on_last_name'
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 980 def rename_index(table_name, old_name, new_name) old_name = old_name.to_s new_name = new_name.to_s validate_index_length!(table_name, new_name) # this is a naive implementation; some DBs may support this more efficiently (PostgreSQL, for instance) old_index_def = indexes(table_name).detect { |i| i.name == old_name } return unless old_index_def add_index(table_name, old_index_def.columns, name: new_name, unique: old_index_def.unique) remove_index(table_name, name: old_name) end
rename_table(table_name, new_name, **) Link
Renames a table.
rename_table('octopuses', 'octopi')
table_alias_for(table_name) Link
Truncates a table alias according to the limits of the current adapter.
table_comment(table_name) Link
Returns the table comment that’s stored in database metadata.
table_exists?(table_name) Link
Checks to see if the table table_name
exists on the database.
table_exists?(:developers)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 59 def table_exists?(table_name) query_values(data_source_sql(table_name, type: "BASE TABLE"), "SCHEMA").any? if table_name.present? rescue NotImplementedError tables.include?(table_name.to_s) end
table_options(table_name) Link
tables() Link
Returns an array of table names defined in the database.
use_foreign_keys?() Link
view_exists?(view_name) Link
Checks to see if the view view_name
exists on the database.
view_exists?(:ebooks)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 74 def view_exists?(view_name) query_values(data_source_sql(view_name, type: "VIEW"), "SCHEMA").any? if view_name.present? rescue NotImplementedError views.include?(view_name.to_s) end